Gilding metal is not copper
Problems with copper factory ammo...
- Thread starter BigPat
- Start date
I'm just going through this process at the moment but in 6mm. The thinking is still relevant for you I believe. I'm no resident expert, but I'm bored so I've played with the numbers for you. The alternative is what the Mrs has on the telly, which isn't good 
I started by looking at the max range I wanted to shoot over. Call it 300m. In my experience TSX/TTSX/GMX bullets really need to have a TV of 2400 fps to expand efficiently and reliably - I know the manufacturers say it's lower than that but that's not my experience of that of many others - maintaining velocity is key to making copper bullets reliable. To work out the MV you need to achieve that 2400 fps TV you need to factor in the BC of the bullet.
Take your .308 with a 130 TTSX. If you can launch it at 3250 fps you will get 2400 fps at 300m. Look at the 26" barrel velocity Barnes claim on their ammunition and it's 3150 fps. So that's not going to work. The range limit with a 26" barrel will be about 260m. If you want to run a 22" barrel the velocity will drop to around 3000 fps and effective range will be down to about 220m.
Run the numbers again with a 150gr TTSX and they claim a MV of 2900 fps with a 26" barrel, probably down to around 2750 fps with a 22" barrel. Plug in the numbers and your effective range with the 22" is around 180m if you want to maintain your 2400 fps.
Alternatively, the most effective is likely to be the 110gr, but I don't think you could find that as factory loaded ammunition. That should get launched at around 3300/3350 fps and will still carry 2400 fps at 300m.
In terms of twist rates, the stability calculator says you will run the standard 12 twist with the 110's and 130's, 150's will need 11. The 165's your currently running should be at 10 twist.
I've shot quite a few deer with 7mm 120 TTSX at 3400 fps and 6.5mm 100 TTSX. The 7mm were mainly Red and Sika, the 6.5mm Fallow and Roe and a few red hinds. I found them to be a very reliable and effective bullet, quick killing and much less carcass damage than traditional lead bullets. I'm confident enough with them to be looking at a 6mm at the moment to shoot Fallow and Roe with the 80 TTSX. I wouldn't hesitate to use the 130gr TTSX in 30 cal on Red, but I would keep barrel length to at least 24" and limit range to 250m.
I started by looking at the max range I wanted to shoot over. Call it 300m. In my experience TSX/TTSX/GMX bullets really need to have a TV of 2400 fps to expand efficiently and reliably - I know the manufacturers say it's lower than that but that's not my experience of that of many others - maintaining velocity is key to making copper bullets reliable. To work out the MV you need to achieve that 2400 fps TV you need to factor in the BC of the bullet.
Take your .308 with a 130 TTSX. If you can launch it at 3250 fps you will get 2400 fps at 300m. Look at the 26" barrel velocity Barnes claim on their ammunition and it's 3150 fps. So that's not going to work. The range limit with a 26" barrel will be about 260m. If you want to run a 22" barrel the velocity will drop to around 3000 fps and effective range will be down to about 220m.
Run the numbers again with a 150gr TTSX and they claim a MV of 2900 fps with a 26" barrel, probably down to around 2750 fps with a 22" barrel. Plug in the numbers and your effective range with the 22" is around 180m if you want to maintain your 2400 fps.
Alternatively, the most effective is likely to be the 110gr, but I don't think you could find that as factory loaded ammunition. That should get launched at around 3300/3350 fps and will still carry 2400 fps at 300m.
In terms of twist rates, the stability calculator says you will run the standard 12 twist with the 110's and 130's, 150's will need 11. The 165's your currently running should be at 10 twist.
I've shot quite a few deer with 7mm 120 TTSX at 3400 fps and 6.5mm 100 TTSX. The 7mm were mainly Red and Sika, the 6.5mm Fallow and Roe and a few red hinds. I found them to be a very reliable and effective bullet, quick killing and much less carcass damage than traditional lead bullets. I'm confident enough with them to be looking at a 6mm at the moment to shoot Fallow and Roe with the 80 TTSX. I wouldn't hesitate to use the 130gr TTSX in 30 cal on Red, but I would keep barrel length to at least 24" and limit range to 250m.
That’s great info Nigel,
My old Sako is a 1/11 twist and a 22.5” ish barrel so the 150gr Fox bullets that I have loaded up may well work fine. But I do like the TTSX, I use the 120gr in my 6.5swede and they are brilliant on everything from Fox to large Fallow.
My old Sako is a 1/11 twist and a 22.5” ish barrel so the 150gr Fox bullets that I have loaded up may well work fine. But I do like the TTSX, I use the 120gr in my 6.5swede and they are brilliant on everything from Fox to large Fallow.
baguio
Well-Known Member
Nigel, any chance that you could write down how you do the calculations?I'm just going through this process at the moment but in 6mm. The thinking is still relevant for you I believe. I'm no resident expert, but I'm bored so I've played with the numbers for you. The alternative is what the Mrs has on the telly, which isn't good
You sound like you are a resident expert to me!
To get the TV you need a ballistic app on your phone. There are lots of options out there, I happen to use Strelok and Applied Ballistics, but Strelok is probably the easiest, and it's free. There are online calculators as well, but I find Strelok simple to use and the easy option. Other people will use different calculators but they all give close enough to the same answerNigel, any chance that you could write down how you do the calculations?
You sound like you are a resident expert to me!
When you set up your gun/bullet combination in Strelok, and input the MV it will give you a table of velocity out as far as you like. It also gives you energy, drop, wind drift etc. If you input 3 bullets of different weights you can see the differences in how each performs as you get down range very easily. Great for comparing say 110/130/150/165 in a 308.
Providing you have put the twist rate of your rifle into Strelok it will also give you the bullets SF (Stability Factor). You're looking for an SF greater than 1.4, preferably 1.5 or higher. You can "over stabilise" a bullet and spinning them too fast just tends to loose velocity and promote spin drift, so ideally keeping the SF below 2 is good. Not a drama if you get to 2.2, but 2.5 is going to be too much.
There are other ways of doing it, but that's my down and dirty simple method and it usually works well.
HAve you a link? I can only see 8mm ones
Thanks, you learn something every day. Has anyone demonstrated that these harder copper bullets don't cause barrel damage?
In theory it should be less wear not more wear . However its the heat of combustion that burns barrels not friction . Barrel steel is significantly harder and more abrasion resistant than copper . The copper again has less contact points than a lead bullet .
Always a tough one to answer because no two barrels and no two loads are tge same and cadence of fire likewise. I suggest if you only shoot copper , don't use double base powder like vhit 5 series you will get many years out of a stalking rifle
Or you could tune your rifle with one of Allan's new moderator/tuners. Scroll down to Feb 13th.
www.facebook.com
Alan Maughan Rifles
Alan Maughan Rifles. 1,456 likes. Precision engineered rifles of all kinds built to benchrest standards
www.facebook.com
Similar threads
